Electrochemical or Double Layer Capacitors (DLC), also referred to as “Supercapacitors”, have gained wide acceptance in the art for providing a unique combination of characteristics, particularly high voltage, power, and capacitance densities. DLCs are an excellent compromise between dielectric capacitors, such as ceramic, tantalum, film, and batteries. DLCs are widely used in high power, pulse applications, such as in GSM, GPRS Edge, and PCS based systems, generally requiring several amps of current for a few milliseconds. DLCs are commonly used in combination with a battery to provide high momentary current requirements, with the battery providing the bulk total energy to the system and a trickle charge to the DLC when high current pulses are not required.
DLCs are generally subject to two limitations: high ESR (equivalent series resistance) and high capacitance loss when use to supply very short duration current pulses. The instant voltage drop experienced when a capacitor delivers a short current pulse is caused by and is directly proportional to the device's ESR. The continuing voltage drop over the duration of the pulse is a function of the available charge, i.e., capacitance. This combination produces a total voltage drop that may make the device unacceptable for certain applications. The voltage drop in a circuit is critical because the circuit will not operate below a certain cut-off voltage. A device's ESR cannot be reduced below a certain inherent value and, thus, high capacitance is needed to minimize total voltage drop. Such higher value capacitance, even with a higher corresponding ESR, results in a lower total voltage drop. A low voltage drop also minimizes conductive and emitted electromagnetic interference.
Conventional dielectric capacitors are typically mounted on a PCB using relatively high speed “pick and place” processes well known to those skilled in the art. The devices are then subjected to IR reflow, vapor phase or wave soldering techniques to complete the mounting process. DLCs, on the other hand, are mounted to a PCB by a hand soldering method using either a soldering iron gun, resistance, or pulse soldering equipment. This hand soldering step is an obvious detriment to efficient production of electronic components requiring a DLC. Conventional wisdom in the art holds that the hand soldering step is necessary to prevent high thermal stresses from being induced in the leads from conventional reflow and automatic soldering processes, and to maintain the device's mounted ESR at an acceptable level. Conventional connector arrangements that might be used to mount a DLC add an unacceptable contribution to ESR because of the lines and traces used for the socket/connector.
Thus, a need exists in the art for a high power electrochemical DLC that may be mounted onto a PCB without hand soldering and without a prohibitive increase in ESR. The present invention provides a solution to this need.